|Year : 2017 | Volume
| Issue : 1 | Page : 3-14
Molecular mediators and controlling mechanism of vascular calcification
Leta Melaku1, Andualem Mossie2
1 Department of Biomedical Sciences, College of Health Sciences, Arsi University, Asela, Ethiopia
2 Department of Biomedical Sciences, College of Public Health and Medical Sciences, Jimma University, Jimma, Ethiopia
|Date of Submission||11-Jan-2017|
|Date of Decision||15-Feb-2017|
|Date of Acceptance||22-Feb-2017|
|Date of Web Publication||9-Mar-2017|
Department of Biomedical Sciences, College of Health Sciences, Arsi University, Asela
Source of Support: None, Conflict of Interest: None
Bone formation involves hydroxyapatite crystals, whose development begins in matrix vesicles that bud from osteoblasts. Vascular smooth muscle cells that have undergone osteoblast differentiation are also able to release similar vesicles with shared protein content. Such differentiation is restrained or inhibited under normal conditions, and there is a balance with osteoclast differentiation experienced by monocytes and macrophages within the vascular wall. Moreover, the reaction which allows crystal growth is thermodynamically unfavorable and is inhibited by pyrophosphate. In some situations, physiological balance is broken and vascular calcification (VC) is able to progress. VC has traditionally been considered to be a passive process that was associated with advanced age, atherosclerosis, uncommon genetic diseases, and some metabolic alterations such as diabetes mellitus and end-stage kidney failure. However, in the last years, VC has been proven to be an active and regulated process, similar to bone mineralization, in which different bone-related proteins are involved. VCs are actively regulated biological processes associated with crystallization of hydroxyapatite in the extracellular matrix and in cells of the media or intima of the arterial wall. Both patterns of VC often coincide and occur in patients with type II diabetes, chronic kidney disease, and other less frequent disorders; VCs are also typical in senile degeneration. Recent results question the classic classification of VC into intimal and medial calcification, at least in capacitance arteries. Pro- and anti-calcifying mechanisms play an active role in calcium deposit ion in vascular cells, making this area an active focus of research.
Keywords: Controlling Mechanism, molecular mediators, vascular calcification
|How to cite this article:|
Melaku L, Mossie A. Molecular mediators and controlling mechanism of vascular calcification. Int J Clin Exp Physiol 2017;4:3-14
|How to cite this URL:|
Melaku L, Mossie A. Molecular mediators and controlling mechanism of vascular calcification. Int J Clin Exp Physiol [serial online] 2017 [cited 2017 Aug 16];4:3-14. Available from: http://www.ijcep.org/text.asp?2017/4/1/3/201791
| Introduction|| |
Bone formation involves hydroxyapatite [Ca10(PO4)6(OH)2] crystals, whose development begins in matrix vesicles (MVs) that bud from osteoblasts. Vascular smooth muscle cells (VSMCs) that have undergone osteoblast differentiation are also able to release similar vesicles with shared protein content. Such differentiation is restrained or inhibited under normal conditions, and there is a balance with osteoclast differentiation experienced by monocytes and macrophages within the vascular wall. Moreover, the reaction which allows crystal growth is thermodynamically unfavorable and is inhibited by Calcification Inhibitors. In some situations, physiological balance is broken and vascular calcification (VC) is able to progress. Occurrence of VC is not new. It has been discovered in the “Iceman” who lived 5000 years ago, and thscientists had already paid attention to this phenomenon and to its relation with renal disease in the 19th century. VC occurs when vessel and/or valvular tissue becomes mineralized. Conventionally, calcification has been classified depending on where the calcium was deposited. In this way, arterial calcification has been divided into intimal calcification (associated with atheromatous plaques ) and medial calcification (known as Mönckeberg's sclerosis) linked to vascular stiffness due to the mineralization of elastic fibers and atherosclerosis seen with age, diabetes, and chronic kidney disease (CKD). Calcification of the intimal layer is reflective of atherosclerotic heart disease. Calcium deposition in the intimal layer of the coronary arteries (known as coronary artery calcification) can lead to vascular occlusion. It is detectable in ~30% of adults without clinical CVD ,,, and is incrementally predictive of future cardiovascular events and overall mortality, independent of traditional CVD risk factors.,, Certain patient groups, especially those with CKD, are at greater risk for coronary artery calcification.,, In 2004, it was determined that 11% of the general population in the United States had CKD, translating into >19 million affected people. CKD is defined as the presence of kidney damage with or without reduced kidney function. The severity of CKD is determined by a staging process that is based on an estimated glomerular filtration rate. Moderate to severe CKD (Stages 3–5) is represented by an estimated glomerular filtration rate of < 60, <30, and <15 mL/min, respectively, and Stage 5b encompasses those individuals who require a form of kidney replacement therapy (hemodialysis [HD], peritoneal dialysis, or kidney transplant).
At every stage of CKD, the leading cause of mortality is CVD and patients are more likely to die of a cardiac event than they are to ever require a form of kidney replacement therapy. CKD patients are particularly prone to medial calcification (known as Mönckeberg's sclerosis), which leads to arterial stiffening, elevated systolic pressure, and increased cardiac workload., Medial calcification is predictive of cardiovascular and all-cause mortality in CKD patients, independent of intimal calcification and CVD risk factors., Calcific uremic arteriopathy, also known as calciphylaxis, classically manifests as calcification of cutaneous and subcutaneous arteries with occlusive intimal proliferation and subsequent fat necrosis. VC increases with age and is notably dysregulated in diabetes, dyslipidemia, renal disease, and hypertension. Although the cellular and molecular events leading to calcium deposition in vascular tissue continue to be explored, it is understood to be a highly regulated process.
| Mechanisms of Vascular Calcification|| |
VC is a pathologic response to toxic stimuli involving metabolic substances and/or inflammatory cells.,,,, Historically, VC was considered to be a passive process, the result of Ca 2+ andPions exceeding solubility in tissue fluid, thereby inducing the precipitation and deposition of hydroxyapatite crystals. However, the current thinking has shifted away from this passive theory; VC formation is now considered a complex, actively controlled intracellular molecular process, involving the differentiation of macrophages and VSMCs into osteoclast-like cells, similar to that which occurs in bone formation.,,, The underlying pathophysiological mechanisms resulting in VC can be broadly described as (1) elevation in serum Ca 2+ andP levels, (2) induction of osteogenesis, (3) inadequate inhibition of the mineralization process, and (4) migration and differentiation of macrophages and VSMCs into osteoclast-like cells.,,, Genetic predisposition certainly plays an important role in the genesis of this phenomenon. According to Rutsch et al., 40%–50% of cases of coronary calcification can be attributed to genetics. Genes ENPP1 and NT5E are, respectively, implicated in infancy and idiopathic VC. The first one encodes a protein which transforms ATP to adenosine and PPi (inhibitor of calcification) whereas the second one converts adenosine monophosphate into adenosine and inorganic phosphate (Pi, accelerator of mineralization).
The VC phenotype caused by mutations in these genes underlines the role of PPi and Pi in pathogenesis. Mutations in ABCC6, a gene encoding a nucleoside-sensitive transporter, have also been linked to hereditary calcification. Alternative action of ABCC6 may include deficient hepatic production of inhibitory factor of matrix Gla protein (MGP), an important inhibitor of calcification., Another major mechanism of development of VCs is similar to that of bone formation  [Figure 1]. First, VSMCs undergo osteogenic differentiation into phenotypically distinct osteoblast-like cells., In case of renal failure, Pi plays a key role in this mechanism.,In vitro, high extracellular Pi concentrations induce a rise in intracellular Pi concentration which is actively mediated by Pit-1, a sodium dependent Pi cotransporter., This increasing Pi concentration in the VSMC induces a phenotypic switch of VSMCs into osteoblast-like cells.,, The protein core-binding factor subunit 1α/runt-related transcription factor 2 (Cfba1/Runx2) is a specific and indispensable transcriptional regulator for this osteoblastic differentiation. Its expression is also enhanced with high extracellular Pi.,, These new cells will express alkaline phosphatase (ALP), secrete, under the control of Cfba1, bone-associated proteins (such as osteopontin [OPN], collagen type 1, osteoprotegerin [OPG], bone morphogenetic protein-2 [BMP-2] and osteocalcin [OC],), and release mineralization-competent MVs in the extracellular matrix.,, VSMCs release MVs under normal physiological conditions and these MVs are protected from mineralization by the presence of calcification inhibitors. Under pathological conditions, a combination of factors makes the MVs mineralization competent. Moreover, an increase of intracellular Pi level mediated by Na/Pi transporter is thought to induce VSMC apoptosis through an unclear process that possibly involves a disruption in mitochondrial metabolism. Some studies suggest that apoptosis leads to calcification.,, The MVs, in which pro-apoptotic factor BCL2-associated X protein has been identified, may be remnants of apoptotic cells. As MVs have the capacity to concentrate and crystallize calcium, apoptosis could be a key regulator of VC. More recently, a different point of view has emerged according to which phenotypically distinct osteoblast-like cells might originate from stem cells rather than VSMCs. A new mechanism called “circulating cell theory,” suggesting an active role for circulating cells arising from sources such as bone marrow, has been postulated to contribute toward VC.
|Figure 1: Schematic diagram depicting multiple mechanisms leading to vascular calcification|
Click here to view
Under the influence of chemoattractants (released by damaged endothelium for instance), these bone marker-positive cells may home to diseased arteries. Under pathologic conditions such as an imbalance between promoters and inhibitors of VC, this population may further undergo osteogenic differentiation in the lesions, which could promote vessel mineralization., Another recent study has also claimed that multipotent vascular stem cells present in the blood vessel wall might differentiate into osteoblast-like cells. Nevertheless, this point of view is still very controversial. Although the role of Pi is well established in osteoblastic differentiation process, many other factors can influence this phenotype conversion and accurate causal mechanisms remained not completely understood. Under normal conditions, VSMCs produce endogenous inhibitors of calcification such as MGP, OPN, OPG, and PPi. A long-term exposure of VSMCs to a variety of stresses can overwhelm the action of these inhibitors and induce differentiation. Among these chronic stresses, ionic disorders (especially hyperphosphatemia and hypercalcemia) are incriminated, but inflammation, hormonal perturbation, metabolic disorders, and oxidative stress can also lead to VC. Oxidative stress in VSMCs, in particular generated by hyperlipidemia and oxidized lipoproteins or uremic milieu, causes the expression of Runx2, osterix and governs Wnt signaling, leading to osteogenic differentiation. Inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), can also induce calcification through Msx2/Wnt/β-catenin pathway. In support of that, calcium deposits colocalize with inflammatory cells in vitro, and in vivo. Moreover, it has been suggested that mineral crystals may themselves be pro-inflammatory, creating a vicious cycle of inflammation and calcification., The receptor for advanced glycation end products (RAGE) endogenously expressed in endothelial cells and its ligands (in which S100 family proteins are found) is also known to be involved in atherosclerotic formation and VC. It has been suggested that galectin-3 and RAGE modulate vascular osteogenesis in part through Wnt/β-catenin signaling. Several trials have shown a raise in serum levels of S100/calgranulins in vascular disease., Thereby, S100 proteins could be a potential biomarker and therapeutic target to develop. Involved in the control of both parathyroid hormone (PTH) and calcitonin secretion, the calcium-sensing receptor (CaSR) is a G protein–coupled cell surface receptor that is able to sense extracellular calcium ions. Evidence has been provided to demonstrate that a decrease in the CaSR protein expression in the vasculature is directly involved in the development of VC.,
It is of particular interest to note that calcimimetics, which are allosteric drug compounds that selectively target the CaSR, decrease VC at least in part through local control of the CaSR expression in VSMC., However, so far, the mechanism whereby the CaSR exert its protective effect remains largely unknown. Hormones have pleiotropic effects on calcific vasculopathy. For example, the adipose-derived factor, leptin, promotes VC in vitro and in vivo. Adiponectin-deficient mice have increased VC. The influence of PTH is a part of bone turnover process. A disruption between promoters and inhibitors can also generate VC. Moreover, similar to bone formation, there might a balance between VC and its resorption. Indeed, monocytes and macrophages contained in the calcified wall can differentiate into an osteoclast-like phenotype and counteract the action of VSMCs that have undergone osteoblast differentiation. Hyperphosphatemia would disadvantage osteoclast phenotype by downregulating receptor activator of nuclear factor-kappa B (NF-κB) ligand (RANKL)-induced signaling, but this is not clear whether osteoclast-like cells can really counteract VC or solely witness vascular remodeling process. All these modifications will favor for an optimal microenvironment for hydroxyapatite formation and calcification. Similar osteogenic differentiation is also observed, in vivo, in animal and human uremic models.,,
| Biomarkers|| |
Under normal conditions, blood vessel cells express mineralization-inhibiting molecules. The loss of their expression, as happens in CKD, causes what is known as “loss of natural inhibition,” giving rise to spontaneous calcification and increased mortality. A list of these calcification-inhibiting molecules has been drawn up after mutation analysis on mice, including among others.
Fibroblast growth factor-23 and Klotho
Fibroblast growth factor-23 (FGF-23) is an approximately 30 kDA protein released by bone that requires the presence of the cofactor Klotho for its classical effects. FGF-23 promotes Pi excretion by reducing its proximal reabsorption by reducing the expression of NPT2a and NPT2c mRNA, sodium/Pi transporters. FGF-23 also decreases conversion of calcidiol into its active form by reducing 1α-hydroxylase activity. Thereby, gastrointestinal absorption of calcium and Pi is reduced. In parathyroid glands, FGF-23 decreases PTH secretion and parathyroid cell proliferation. FGF-23 null mice develop hypercalcitriolemia and VC. Although the mechanistic link remains to be explained, FGF-23 may serve as a novel risk marker for the cardiovascular mortality in CKD. In patients with coronary artery disease (CAD), the same independent link between FGF-23 and mortality has been demonstrated. In contrast to FGF-23, Klotho excess has never been shown to be noxious. Interestingly, Klotho levels are upregulated by Vitamin D receptor agonists (calcitriol or paricalcitol) in CKD mice submitted to a high Pi diet. These mice show half less calcification than those who did not receive therapy. Phosphaturia is increased whereas phosphatemia and FGF-23 levels are lowered. In contrast, vascular Klotho deficiency favors the development of arterial calcification and mediates resistance to beneficial vascular effects of FGF-23.
Fetuin-A (Fet-A) is a serum 59-kDa glycoprotein that inhibits ectopic VC, produced by the liver that possess a systemic action.,
It is a powerful inhibitor of hydroxyapatite formation, reducing the formation of crystals in in vitro solutions containing calcium and phosphorus without affecting those that are already formed., Mice that are deficient in this protein develop extensive calcifications in soft tissue such as the myocardium, kidneys, tongue, and skin. Fet-A is thought to inhibit calcification by binding early calcium Pi crystals and by inhibiting crystal growth and mineral deposition. This could be facilitated by the formation of large calciprotein particles (CPPs)., Indeed, the accumulation of naked calcium Pi crystals is responsible for extraosseous calcification and causes inflammation. These crystals are usually digested by the cells of the reticuloendothelial system such as macrophages. In contact with the crystals, macrophages secrete pro-inflammatory cytokines and undergo more apoptosis. The formation of Fet-A CPP facilitates the clearance of these crystals and thereby reduces their negative impact. Fet-A likely plays a very important role in the stabilization of these complexes and reduces the inflammatory response. Fet-A binds and sequesters insoluble mineral nuclei, forming soluble colloidal CPP, thereby inhibiting crystal growth and aggregation. Macrophages secrete less cytokines and undergo less apoptosis phenomenon as compared to reactions caused by naked crystals. This property of Fet-A to decrease inflammation may be influenced by the phosphorylation degree of the glycoprotein. In these studies, lower serum Fet-A concentrations have been associated with increases in calcification scores, arterial stiffness, mortality, and incidence of cardiovascular events.,,,,
OPN is a phosphoprotein that is usually found in mineralized tissue such as bones and teeth., It inhibits mineralization by blocking hydroxyapatite formation and activating osteoclast function. Although it is not found in normal arteries, its expression is detected in atherosclerotic plaques and calcified vessels. OPN knock-out mice do not develop VC, but when these mice are bred with MGP knock-out mice, the VCs are more important than in simple MGP knock-out mice. OPN must be phosphorylated to act as a calcification inhibitor., OPN inhibits mineralization of VSMC by binding to the mineralized crystal surface. On the contrary to the fully phosphorylated OPN, cleaved OPN could act as a pro-inflammatory cytokine and a pro-angiogenic factor facilitating vascular mineralization.,
The possibility that OPN could serve as a calcification serum marker is controversial. Berezin and Kremzer showed that OPN was a good predictor of coronary calcification in type II diabetes mellitus patients. Tousoulis et al. found a positive association between OPN and arterial stiffness in CAD. Indeed, the discrepancy between the different studies may perhaps be explained by the differences in patient populations. It is thought that OPN plays a key role in inflammatory process. Its relation with diseases related to inflammation such as atherosclerosis, obesity and autoimmune diseases has already been shown.,,,, It has also been suggested that hyperglycemia could upregulate OPN and thereby lead to VSMCs proliferation.
OPG is a member of the TNF receptor family that has been identified as a regulator of bone resorption. OPG is produced by many tissues, including cardiovascular system, lungs, kidney, and immune system. OPG is a regulatory factor produced by bone marrow-derived stromal cells. OPG plays a pivotal role in the regulation of the bone turnover, inhibiting osteoclast differentiation and acting as a decoy receptor for the RANKL system. It interferes with the interaction between RANK (expressed by osteoclast-like cells) and RANKL (expressed by osteoblast-like cells). OPG is also thought to inhibit ALP activity. OPG levels are significantly higher in CKD patients, in relation to the severity of renal failure. Although OPG is known to impede osteoclast differentiation in bone, OPG is usually considered as a protective factor against VC as it blocks the bone remodeling process in the vascular tissue. OPG is also a neutralizer of the pro-apoptotic actions of TNF-related apoptosis-inducing ligand, which strongly activates vascular cells apoptosis. Apoptotic bodies can also lead to mineralization. In support of that, it has been observed that OPG-deficient mice do develop both severe aortic calcifications and osteoporosis., Interestingly, OPG seems to be a marker of VC onset rather than a severity or progression predictor.,
OC, a Vitamin-K-dependent matrix protein that inhibits calcium salt precipitation in vitro, shows a strong affinity for hydroxyapatite. OC has been found in calcified atherosclerotic plaques and calcified aortic valves. It was generally thought that OC inhibits crystal growth  and limits bone formation. Nonetheless, its utility as serum marker is still discussed in conflicting studies. Aoki et al. did not show any relationship between OC and VC in type II diabetes mellitus patients whereas Kim et al. found an inverse correlation between OC and Agatston calcification score in Asian women, even after adjusting for age. To define if OC can be used as a diagnostic or a screening tool, the role of OC in the pathogenesis of VC clearly remains to be clarified.
PPi is a small molecule made of two Pi ions. It acts as a calcification inhibitor by inhibiting hydroxyapatite crystal formation. Once again, knock-out mice (in fact, knock-out mice for a precursor) develop VCs. Absence of PPi would promote VSMC differentiation, but the mechanism is not fully understood., O'Neill et al. demonstrated the negative association between PPi and VC in CKD. Although the short half-life of PPi limits the possibility for improving VC by bolus injections, daily peritoneal dialysis achieved with a solution which contains PPi in CKD mouse model do succeed in inhibiting calcification. O'Neill et al. demonstrated that daily intraperitoneal injections in rats could also reduce both incidence and amount of calcification. PPi has been shown to inhibit mineralization on rat aortic VSMCs cultures too. Furthermore, bisphosphonates, nonhydrolysable analogs of PPi, have also proved their ability to inhibit aortic calcifications in experimental renal failure rats. Calcification was stopped in cultures of rat aortas as well as in vivo model. It supports the idea that bisphosphonates have direct effects on VC, independent of bone, maybe through a downregulation of Notch1-RBP-Jκ signaling pathway and MsX2 gene induction. ATP, which is a polyphosphate associated with nucleoside, might also act as calcium Pi deposition inhibitor, not only as the source of PPi but also as a direct inhibitor. Even if PPi seems to be a promising marker, its determination has been performed in a single center only and the transferability to other centers should be validated.
Matrix Gla protein
MGP is a Vitamin K, 14-kDa γ-carboxylated protein expressed by chondrocytes, VSMCs, endothelial cells, and fibroblasts. Its role as a calcification inhibitor has been illustrated by MGP knock-out mice that develop extensive arterial calcifications., In 2002, Moe et al. demonstrated a correlation between vascular MGP expression and the calcification of epigastric arteries in dialysis patients., MGP-deficiency in humans leads to Keutel syndrome, a rare genetic disease hallmarked by abnormal soft tissue calcification. MGP binds calcium crystals, inhibits crystal growth, and plays a role in the normal phenotype of VSMCs in preventing the osteoblastic differentiation., MGP also binds and inactivates a pro-mineralization factor, BMP-2. Among other effects, BMP-2 promotes osteogenic conversion of VSMCs through MSX2 transcription factor. MGP could also protect mineral nucleation sites on elastin and thereby prevent spontaneous calcification of the elastic laminae. In support of that, the irregular calcification of the thoracic and abdominal aorta segments in MGP −/− mice correlates with the local variations of the elastin content. Parallel to this study, other authors hypothesized a mineralization process by size exclusion, in which MGP proves to be essential to prevent mineralization within fibrils.
There are studies that speculate that, as well as hyperphosphatemia and hypercalcemia, there are substances present in the blood serum of patients with CKD capable of stimulating calcification. Bovine VSMC in the presence of uremic serum increases the expression of calcification-related proteins. A large number of uremic factors have been identified that are capable of inducing osteogenic genes, transforming osteoblasts, and secreting some bone matrix proteins in the walls of blood vessels and soft tissue. Some of these factors are TNF, inflammatory cytokines, fibronectin, type-I collagen, and 25-hydroxycholesterol. These uremic serum substances stimulate the expression of molecules essential to vesicular calcification.
ALP is one of the osteoblastic phenotype markers and is considered essential in the VC process. It has been detected in vascular and heart valve calcifications. ALP expressed on the surface of cells can act on Pi liberators, releasing inorganic Pi. Inflammatory cytokines and Vitamin D induce its upregulation and mineralization.,
Core-binding factor alpha 1
Core-binding factor alpha 1 (Cbfa1) is the main regulator of bone cell differentiation. Cbfa1-deficient mice have problems with cartilage formation and bone mineralization. It acts as a transcription factor that accelerates the expression of important osteoblast lineage genes such as OC, OPN, ALP, or type-I collagen. Its expression is upregulated by Pi43 and uremic toxins.
Bone morphogenetic protein-2
BMP are a group of, at least, 30 proteins that receive their name from their osteoinductive properties. BMPs belong to a subdivision of TGF-β-like growth factors family. BMPs regulate growth, differentiation, and development in the embryo as well as during tissue remodeling processes in the adult organism. BMP-2 is an important molecule in the regulation of bone formation as well as in VC., In bone, it promotes osteoblast differentiation and mineralization. Inhibition of BMP-2 inhibits osteoblast differentiation and bone formation in vivo and in vitro and protects against atherosclerosis and VC. They act by binding to a heterodimeric system of transmembrane receptors (BMP-1 and BMP-2 receptor) that trimerises upon binding. The binding of a BMP to its specific type II receptor results in the type 1 receptor being activated. This causes phosphorylation and nuclear translocation of the Smad transcription factors, thus modifying the transcription rate of target genes. They then induce ectopic bone formation.
Sclerostin is an osteocyte-specific glycoprotein and is considered as a potent inhibitor of bone formation., It inhibits specific coreceptors needed for β-catenin-dependant signaling activation. This pathway is involved in osteoblast-mediated bone formation. It is thought that sclerostin plays a role in bone mechanosensibilization. When bone undergoes a substantial strain, sclerostin production would be decreased and bone could thus increase its formation in response to mechanical stress. As β-catenin belongs to Wnt cascade signaling and as Wnt pathway is thought to be implicated in development of VC, it is interesting to investigate a potential association between sclerostin levels and VCs. In non-CKD patients, some studies have demonstrated a positive association between sclerostin levels and VC,, whereas in other ones, there was not a significant correlation between the two parameters.,
Receptor activator of nuclear factor kappa-B ligand
RANKL (also known as osteoprotegerin ligand) is a protein consisting of 316 amino acids with a molecular weight of 38 kD. Its expression is also modulated by several cytokines, glucocorticoids, and PTH., RANKL is produced by osteoblast lineage cells and activated T-cells. It promotes osteoclast formation, fusion, differentiation, activation, and survival, leading to increased bone resorption and bone loss. RANKL stimulates its specific receptor RANK, which is expressed in fewer cells such as progenitor cells and mature osteoclasts, activated T-cells, and dendritic cells.,, The activation of RANK by RANKL triggers the NF-κB intracellular signaling cascade. The final stage of RANK activation is the NK-κB translocation into the nucleus, which can take place by the classical or alternative pathway. Both pathways are regulated by their kinases which are, respectively, IKK and IKKα. The NK-κB translocation to the nucleus modulates the expression of different genes, for example, BMP4. The biological effects of OPG are the opposite of RANKL-mediated effects because OPG acts as a soluble inhibitor that prevents RANKL interaction and the subsequent stimulation of its RANK receptor. Many trials have shown that VC as well as arterial stiffness and cardiovascular events are inversely related to serum RANKL ,, and positively related to serum OPG.,,,,,,,,,,,
| Strategies to Reduce Vascular Calcifications|| |
Any strategy designed to reduce the impact of VCs has to begin with primary prevention measures to control cardiovascular risk factors. In the particular case of CKD, it is imperative to avoid further kidney damage. In this respect, it is crucial to promote a healthy lifestyle, with a balanced diet, regular physical exercise, smoking abstinence, and low alcohol intake. Once VCs appear, secondary prevention must aim to reduce their complications, intensifying previous measures, and initiating the appropriate drug therapy. Theoretically, any kind of intervention aiming to reduce VC should curtail the influence of factors that promote calcifications and/or augment the effects of factors that may inhibit calcifications. Most strategies to reduce VCs have focused on the most common modifiable risk factors such as hyperphosphatemia, hypercalcemia, the CaxP product, hyperparathyroidism, smoking, hyperlipidemia, and hypertension.
Control of hyperphosphatemia, hypercalcemia, and CaxP product
Disturbances in serum phosphorus, calcium, and calcium-phosphorus product are frequently seen in CKD patients and are implicated in the promotion of VC as well as in an increased death risk. Due to the fact that dietary restriction of phosphorus and intermittent dialysis are not usually effective in controlling serum phosphorus, most patients with CKD Stage 5 show a high prevalence of hyperphosphatemia with its known implications in the pathogenesis of secondary hyperparathyroidism, cardiovascular alterations, and mortality. As mentioned before, in vivo and in vitro studies shed light on the role of phosphorus as promoter of VC, demonstrating that the control of phosphorus should be a priority in clinical practice. Calcium Pi binders such as calcium acetate and calcium carbonate have replaced aluminum hydroxide as the most widely prescribed Pi binders. The possible negative role of calcium loading from these binders on the progression of VCs has led to the abandonment of calcium- and aluminum-based Pi-binders in favor of new calcium- or aluminum-free Pi binders (sevelamer hydrochloride and lanthanum carbonate).
These changes in the treatment have reduced hypercalcemic adverse events in comparison to calcium-based binders. An experimental study demonstrated that treatment with sevelamer in rats decreased renal calcification as compared to rats that received calcium carbonate or untreated rats. In addition, a clinical trial showed that sevelamer reduced the progression of both coronary and aortic calcifications compared to calcium carbonate. However, the mechanism of the beneficial effect of sevelamer on the progression of calcification is still not fully understood. One possible mechanism is based on the reduction of the calcium load; however, reduced VCs may also result from reductions in total and low-density lipoprotein (LDL) cholesterol, which occur during treatment with sevelamer.
Control of secondary hyperparathyroidism
The use of Vitamin D metabolites is a challenging subject that still remains controversial. The current treatment of secondary hyperparathyroidism in dialysis patients includes suppression of PTH with supraphysiologic doses of Vitamin D or its analogs. Although it is widely known that a high dosage of Vitamin D metabolites favors the onset and progression of VCs, several studies have paradoxically demonstrated a long-term beneficial effect of Vitamin D on VCs. Low Vitamin D status is associated with a higher prevalence of VCs, bone and mineral disturbances, susceptibility to some infections, higher risk of autoimmune diseases, some malignancies, and many other complications. Observational studies in patients on HD and in the general population have also demonstrated a lower morbidity and a cardiovascular survival advantage in patients who are treated with Vitamin D receptor activators., A major breakthrough in the management of the calcium Pi metabolism of dialysis patients was achieved recently with the introduction of calcimimetics. These compounds were the first agents introduced to lower PTH with advantageous effects on serum calcium and Pi. It has been demonstrated experimentally that the calcimimetic R568 reduces aortic calcifications and mortality in rats, in which aortic calcifications were induced using a high dose of calcitriol. Moreover, another experimental study showed that calcimimetics may even favor the regression of VC.
Control of dyslipidemia
Hyperlipidemia, particularly increased LDL cholesterol, has been implicated in the progression of VCs. In addition, in the general population, the beneficial effect of lowering LDL cholesterol levels on the progression of calcification has been reported by several groups., As mentioned previously, patients who were treated with sevelamer showed a significant decrease in LDL cholesterol levels, which may explain the beneficial effects in the progression of cardiovascular calcification. It is known that the rapid progression of coronary arterial calcification in HD patients is associated with higher triglycerides and lower high-density lipoprotein cholesterol levels.
Control of blood pressure
Hypertension is a modifiable risk factor for VCs in both general population and CKD patients. Several studies in ESRD and essential hypertension have shown that arterial stiffening is an independent predictor of mortality. As arteries become stiffer, the pulse wave velocity increases and it is responsible for a rapid return of wave reflections from the periphery to the ascending aorta during systole, which causes an abnormal rise of aortic systolic blood pressure with decreased diastolic blood pressure and high pulse pressure. Increased wave reflections and high pulse pressure are the independent risk factors for mortality of ESRD patients.
Diabetes is a disease that is known to be complicated by heterogeneous metabolic risk factors, such as hyperglycemia, hyperlipidemia, insulin resistance, glycation, oxidative and carbonic stress, and tissue hypoxia. In the nonuremic population, VC occurs more frequently in diabetics. In CKD patients, VC in diabetics has been reported to be more prevalent and more advanced than in nondiabetics. Several studies emphasize the importance of glycemic control in the prevention of the development and progression of VC in diabetic CKD patients.
| Conclusion|| |
At present, the ideal marker of VC does not exist. The pathophysiological mechanisms underlying this phenomenon are still poorly understood. As explained in the introduction, calcification can be induced by various situations. Etiologies that induce VC in diabetes mellitus patients are likely different from those which lead to the same result in CKD patients or postmenopausal women. Signaling pathways that are involved in VC may then depend on patient's status. A perfect marker would be ideally located on a hypothetical convergence point of all these pathological conditions. Thus, it could reflect reliably calcification emergence and progression in any situation. However, this view is maybe too utopian and simplistic. Over the years, study of biomarkers showed a large variety of conditions that can modulate vascular microenvironment composition, such as bone turnover, inflammation, Vitamin D status, or even oxidative stress. Within this vascular microenvironment itself, a dense and interconnected network of calcification inhibitors and promoters was highlighted as shown in [Figure 1]. (i) VSMCs undergo differentiation into osteoblast-like cells, in great part because of an intracellular Pi increased concentration, likely mediated by the co-transporter Pit-1, in response to extracellular hyperphosphatemia. (ii) Renal failure is one of the major hyperphosphatemia origin whereas(iii) FGF-23 is a factor which tend to moderate it by increasing Pi renal excretion. This FGF-23 action is achieved with Klotho's help. FGF-23 has other effects described, among which noxious ones are also suspected.(iv) Other factors such as BMP-2, absence of PPi (in part, due to ALP activity), oxidative stress, inflammatory process, or metabolic disorders are also known to be responsive to VSMCs conversion. (v) Calcium enhancement also proved to be deleterious, especially by its ability to induce Pit-1 overexpression and also by alteration of MGP and Fet-A actions, two VC inhibitors. (vi) The VSMCs conversion will favor excretion of bone-associated proteins, such as OPN, collagen type 1, BMP-2, and OC and(vii) VSMCs will release mineralization-competent MVs. In turn,(viii) BMP-2 can promote osteoblast differentiation and is a potent calcification inducer.(ix) MGP, expressed by chondrocytes and VSMCs under normal conditions, inactivates BMP-2. It also binds calcium crystals and inhibits crystal growth. Finally, it prevents osteoblastic differentiation too. As OC, its activity is Vitamin-K dependent and can be countered by Vitamin-K antagonists.(x) OC and(xi) osteonectin are known to bind calcium/Pi crystal but their accurate actions as inducers or inhibitors need to be specified, whereas the (xii) PPi inhibiting effect on crystal formation is well known. The recent discovery of OC metabolic effects might suggest OC is a promoter of VSMCs differentiation into osteoblast-like cells.(xiii) OPN activity would depend on its phosphorylation state. Fully phosphorylated OPN would inhibit mineralization by blocking hydroxyapatite formation and activating osteoclast function while the cleaved one could act as a pro-inflammatory cytokine and pro-angiogenic factor facilitating vascular mineralization.(xiv) OPG is considered as a regulatory factor. On one hand, it can prevent VC by blocking bone remodeling process in vascular tissue and by neutralizing the pro-apoptotic actions of TRAIL. It might also inhibit ALP activity. On the other hand, the inhibition of bone remodeling process by OPG could induce a calcium shift into vascular cells. (xv) Fet-A released by the liver inhibits mineralization perhaps through CPP formation while(xvi) PTH secreted by parathyroid enhances calcification phenomenon, as both low and high bone turnover might lead to VC. Under normal conditions, there is a balance between all these parameters. It is possible that each pathological condition disrupts the balance with its own approach. Nevertheless, it seems that all the calcification inhibitors do not possess the same potential. OPG serum levels appear to be correlated repeatedly to calcification in many pathological conditions. However, OPG would not reflect the severity of damages as would FGF-23 do. FGF-23 levels should be followed up, either upwards or downwards, given the suspected duality of the effects of FGF-23. Low serum Fet-A levels are usually associated with VC but an increased CPP fraction of Fet-A would also be useful to reflect a procalcific milieu. Nonfully γ-carboxylated MGP is associated with VC too and might be an interesting marker to monitor patients under AVK treatment. OPN would be an attractive marker in diseases with inflammatory component such as diabetes or autoimmune diseases. Within this category of disease, it might help to reclassify asymptomatic subjects with classical risk factors into high-risk group for further examination. In population with renal deficiency, particularly susceptible to develop VC, the problem becomes even more complex. Whether patients undergo dialysis or not, reference values will need to be adapted, depending on renal failure severity and marker ability to be removed by dialysis. In addition, as described earlier, complex interactions exist between different actors (pro or anti-calcifications) such as PTH, Vitamin D, FGF-23, OPG, sclerostin, acting sometimes through redundant signaling pathways such as Wnt/β-catenin, Runx2/Cbfa1, and Notch1-RBP-Jκ. Furthermore, these interactions could be different according to the stage of CKD. Thus, the stage of disease should be taken into account in the interpretation of biomarker and/or the combination of biomarkers. As evidenced by the present discussion, VC physiopathology is still far from being fully elucidated. The role of each biomarker needs to be clarified and many studies are still leading to contradictory results.In vitro observations are sometimes very different from conclusions observed in in vivo studies. Direct effects on vasculature and indirect effects mediated by bone turnover are not easy to discriminate. When a correlation between the serum levels of a calcification marker and calcification is clearly showing up, it still remains to determinate whether level fluctuations attest a noxious effect of the biomarker or if they highlight a compensatory process or even solely reflect phenomenon as bystander. Qualities that would be appreciated for selecting a good marker depend on its capacities to achieve clinical goals, particularly its ability to select high-risk patients for further investigation, to make a reliable calcification assessment, to provide a prognostic, to help in treatment choice, or to follow-up the treatment efficiency. Given importance to assess and control mineralization process, it is essential to keep going on building up more and more knowledge.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Kapustin AN, Davies JD, Reynolds JL, McNair R, Jones GT, Sidibe A, et al.
Calcium regulates key components of vascular smooth muscle cell-derived matrix vesicles to enhance mineralization. Circ Res 2011;109:e1-12.
Hofmann Bowman MA, McNally EM. Genetic pathways of vascular calcification. Trends Cardiovasc Med 2012;22:93-8.
Murphy WA Jr., Nedden Dz Dz, Gostner P, Knapp R, Recheis W, Seidler H. The iceman: Discovery and imaging. Radiology 2003;226:614-29.
Virchow R. Cell theory and neoplasia. Arch Pathol Anat 1855;8:103-13.
Burke AP, Taylor A, Farb A, Malcom GT, Virmani R. Coronary calcification: Insights from sudden coronary death victims. Z Kardiol 2000;89 Suppl 2:49-53.
Edmonds ME, Morrison N, Laws JW, Watkins PJ. Medial arterial calcification and diabetic neuropathy. Br Med J (Clin Res Ed) 1982;284:928-30.
Bild DE, Detrano R, Peterson D, Guerci A, Liu K, Shahar E, et al.
Ethnic differences in coronary calcification: The Multi-Ethnic Study of Atherosclerosis (MESA). Circulation 2005;111:1313-20.
Budoff MJ, Gul KM. Expert review on coronary calcium. Vasc Health Risk Manag 2008;4:315-24.
Hoff JA, Daviglus ML, Chomka EV, Krainik AJ, Sevrukov A, Kondos GT. Conventional coronary artery disease risk factors and coronary artery calcium detected by electron beam tomography in 30,908 healthy individuals. Ann Epidemiol 2003;13:163-9.
Hoffmann U, Massaro JM, Fox CS, Manders E, O'Donnell CJ. Defining normal distributions of coronary artery calcium in women and men (from the Framingham Heart Study). Am J Cardiol 2008;102:1136-41, 1141.e1.
Detrano R, Guerci AD, Carr JJ, Bild DE, Burke G, Folsom AR, et al.
Coronary calcium as a predictor of coronary events in four racial or ethnic groups. N Engl J Med 2008;358:1336-45.
Thompson GR, Partridge J. Coronary calcification score: The coronary-risk impact factor. Lancet 2004;363:557-9.
Vliegenthart R, Oudkerk M, Hofman A, Oei HH, van Dijck W, van Rooij FJ, et al.
Coronary calcification improves cardiovascular risk prediction in the elderly. Circulation 2005;112:572-7.
Coylewright M, Rice K, Budoff MJ, Blumenthal RS, Greenland P, Kronmal R, et al.
Differentiation of severe coronary artery calcification in the Multi-Ethnic Study of Atherosclerosis. Atherosclerosis 2011;219:616-22.
Goodman WG, Goldin J, Kuizon BD, Yoon C, Gales B, Sider D, et al.
Coronary-artery calcification in young adults with end-stage renal disease who are undergoing dialysis. N Engl J Med 2000;342:1478-83.
Qunibi WY. Reducing the burden of cardiovascular calcification in patients with chronic kidney disease. J Am Soc Nephrol 2005;16 Suppl 2:S95-102.
Coresh J, Selvin E, Stevens LA, Manzi J, Kusek JW, Eggers P, et al.
Prevalence of chronic kidney disease in the United States. JAMA 2007;298:2038-47.
National Kidney Foundation. K/DOQI clinical practice guidelines for chronic kidney disease: Evaluation, classification, and stratification. Am J Kidney Dis 2002;39 2 Suppl 1:S1-266.
Foley RN, Parfrey PS, Sarnak MJ. Clinical epidemiology of cardiovascular disease in chronic renal disease. Am J Kidney Dis 1998;32 5 Suppl 3:S112-9.
Amann K. Media calcification and intima calcification are distinct entities in chronic kidney disease. Clin J Am Soc Nephrol 2008;3:1599-605.
London GM, Marchais SJ, Guérin AP, Métivier F. Arteriosclerosis, vascular calcifications and cardiovascular disease in uremia. Curr Opin Nephrol Hypertens 2005;14:525-31.
London GM, Guérin AP, Marchais SJ, Métivier F, Pannier B, Adda H. Arterial media calcification in end-stage renal disease: Impact on all-cause and cardiovascular mortality. Nephrol Dial Transplant 2003;18:1731-40.
Zoungas S, Cameron JD, Kerr PG, Wolfe R, Muske C, McNeil JJ, et al.
Association of carotid intima-medial thickness and indices of arterial stiffness with cardiovascular disease outcomes in CKD. Am J Kidney Dis 2007;50:622-30.
Danziger J. Vitamin K-dependent proteins, warfarin, and vascular calcification. Clin J Am Soc Nephrol 2008;3:1504-10.
Hayden MR, Tyagi SC, Kolb L, Sowers JR, Khanna R. Vascular ossification-calcification in metabolic syndrome, type 2 diabetes mellitus, chronic kidney disease, and calciphylaxis-calcific uremic arteriolopathy: The emerging role of sodium thiosulfate. Cardiovasc Diabetol 2005;4:4.
Karwowski W, Naumnik B, Szczepanski M, Mysliwiec M. The mechanism of vascular calcification – A systematic review. Med Sci Monit 2012;18:RA1-11.
Marso SP, Hiatt WR. Peripheral arterial disease in patients with diabetes. J Am Coll Cardiol 2006;47:921-9.
Kaneto H, Katakami N, Matsuhisa M, Matsuoka TA. Role of reactive oxygen species in the progression of type 2 diabetes and atherosclerosis. Mediators Inflamm 2010;2010:453892.
Shanahan CM, Crouthamel MH, Kapustin A, Giachelli CM. Arterial calcification in chronic kidney disease: Key roles for calcium and phosphate. Circ Res 2011;109:697-711.
Rocha-Singh KJ, Zeller T, Jaff MR. Peripheral arterial calcification: Prevalence, mechanism, detection, and clinical implications. Catheter Cardiovasc Interv 2014;83:E212-20.
Sage AP, Tintut Y, Demer LL. Regulatory mechanisms in vascular calcification. Nat Rev Cardiol 2010;7:528-36.
Nitta K. Vascular calcification in patients with chronic kidney disease. Ther Apher Dial 2011;15:513-21.
Shao JS, Cheng SL, Sadhu J, Towler DA. Inflammation and the osteogenic regulation of vascular calcification: A review and perspective. Hypertension 2010;55:579-92.
Giachelli CM. Vascular calcification mechanisms. J Am Soc Nephrol 2004;15:2959-64.
Rutsch F, Nitschke Y, Terkeltaub R. Genetics in arterial calcification: Pieces of a puzzle and cogs in a wheel. Circ Res 2011;109:578-92.
Evrard S, Delanaye P, Kamel S, Cristol JP, Cavalier E; SFBC/SN joined working group on vascular calcifications. Vascular calcification: From pathophysiology to biomarkers. Clin Chim Acta 2015;438:401-14.
Li Q, Jiang Q, Schurgers LJ, Uitto J. Pseudoxanthoma elasticum: Reduced gamma-glutamyl carboxylation of matrix gla protein in a mouse model (Abcc6-/-). Biochem Biophys Res Commun 2007;364:208-13.
Moe SM, Duan D, Doehle BP, O'Neill KD, Chen NX. Uremia induces the osteoblast differentiation factor Cbfa1 in human blood vessels. Kidney Int 2003;63:1003-11.
Giachelli CM. Vascular calcification: In vitro
evidence for the role of inorganic phosphate. J Am Soc Nephrol 2003;14 9 Suppl 4:S300-4.
Jono S, McKee MD, Murry CE, Shioi A, Nishizawa Y, Mori K, et al.
Phosphate regulation of vascular smooth muscle cell calcification. Circ Res 2000;87:E10-7.
Li X, Yang HY, Giachelli CM. Role of the sodium-dependent phosphate cotransporter, Pit-1, in vascular smooth muscle cell calcification. Circ Res 2006;98:905-12.
Steitz SA, Speer MY, Curinga G, Yang HY, Haynes P, Aebersold R, et al.
Smooth muscle cell phenotypic transition associated with calcification: Upregulation of Cbfa1 and downregulation of smooth muscle lineage markers. Circ Res 2001;89:1147-54.
Mizobuchi M, Towler D, Slatopolsky E. Vascular calcification: The killer of patients with chronic kidney disease. J Am Soc Nephrol 2009;20:1453-64.
Giachelli CM, Bae N, Almeida M, Denhardt DT, Alpers CE, Schwartz SM. Osteopontin is elevated during neointima formation in rat arteries and is a novel component of human atherosclerotic plaques. J Clin Invest 1993;92:1686-96.
Levy RJ, Schoen FJ, Levy JT, Nelson AC, Howard SL, Oshry LJ. Biologic determinants of dystrophic calcification and osteocalcin deposition in glutaraldehyde-preserved porcine aortic valve leaflets implanted subcutaneously in rats. Am J Pathol 1983;113:143-55.
Reynolds JL, Joannides AJ, Skepper JN, McNair R, Schurgers LJ, Proudfoot D, et al.
Human vascular smooth muscle cells undergo vesicle-mediated calcification in response to changes in extracellular calcium and phosphate concentrations: A potential mechanism for accelerated vascular calcification in ESRD. J Am Soc Nephrol 2004;15:2857-67.
Kapustin AN, Shanahan CM. Calcium regulation of vascular smooth muscle cell-derived matrix vesicles. Trends Cardiovasc Med 2012;22:133-7.
Kendrick J, Chonchol M. The role of phosphorus in the development and progression of vascular calcification. Am J Kidney Dis 2011;58:826-34.
Giachelli CM, Speer MY, Li X, Rajachar RM, Yang H. Regulation of vascular calcification: Roles of phosphate and osteopontin. Circ Res 2005;96:717-22.
Kim KM. Apoptosis and calcification. Scanning Microsc 1995;9:1137-75.
Kockx MM, De Meyer GR, Muhring J, Jacob W, Bult H, Herman AG. Apoptosis and related proteins in different stages of human atherosclerotic plaques. Circulation 1998;97:2307-15.
Proudfoot D, Skepper JN, Hegyi L, Bennett MR, Shanahan CM, Weissberg PL. Apoptosis regulates human vascular calcification in vitro
: Evidence for initiation of vascular calcification by apoptotic bodies. Circ Res 2000;87:1055-62.
Pal SN, Golledge J. Osteo-progenitors in vascular calcification: A circulating cell theory. J Atheroscler Thromb 2011;18:551-9.
Tang Z, Wang A, Yuan F, Yan Z, Liu B, Chu JS, et al.
Differentiation of multipotent vascular stem cells contributes to vascular diseases. Nat Commun 2012;3:875.
Sutra T, Morena M, Bargnoux AS, Caporiccio B, Canaud B, Cristol JP. Superoxide production: A procalcifying cell signalling event in osteoblastic differentiation of vascular smooth muscle cells exposed to calcification media. Free Radic Res 2008;42:789-97.
Byon CH, Javed A, Dai Q, Kappes JC, Clemens TL, Darley-Usmar VM, et al.
Oxidative stress induces vascular calcification through modulation of the osteogenic transcription factor Runx2 by AKT signaling. J Biol Chem 2008;283:15319-27.
Shao JS, Cheng SL, Pingsterhaus JM, Charlton-Kachigian N, Loewy AP, Towler DA. Msx2 promotes cardiovascular calcification by activating paracrine Wnt signals. J Clin Invest 2005;115:1210-20.
Lee HL, Woo KM, Ryoo HM, Baek JH. Tumor necrosis factor-alpha increases alkaline phosphatase expression in vascular smooth muscle cells via MSX2 induction. Biochem Biophys Res Commun 2010;391:1087-92.
Tintut Y, Patel J, Parhami F, Demer LL. Tumor necrosis factor-alpha promotes in vitro
calcification of vascular cells via the cAMP pathway. Circulation 2000;102:2636-42.
Tintut Y, Patel J, Territo M, Saini T, Parhami F, Demer LL. Monocyte/macrophage regulation of vascular calcification in vitro
. Circulation 2002;105:650-5.
Aikawa E, Nahrendorf M, Figueiredo JL, Swirski FK, Shtatland T, Kohler RH, et al.
Osteogenesis associates with inflammation in early-stage atherosclerosis evaluated by molecular imaging in vivo
. Circulation 2007;116:2841-50.
Shanahan CM. Inflammation ushers in calcification: A cycle of damage and protection? Circulation 2007;116:2782-5.
Smith ER, Ford ML, Tomlinson LA, Rajkumar C, McMahon LP, Holt SG. Phosphorylated fetuin-A-containing calciprotein particles are associated with aortic stiffness and a procalcific milieu in patients with pre-dialysis CKD. Nephrol Dial Transplant 2012;27:1957-66.
Menini S, Iacobini C, Ricci C, Blasetti Fantauzzi C, Salvi L, Pesce CM, et al.
The galectin-3/RAGE dyad modulates vascular osteogenesis in atherosclerosis. Cardiovasc Res 2013;100:472-80.
Averill MM, Kerkhoff C, Bornfeldt KE. S100A8 and S100A9 in cardiovascular biology and disease. Arterioscler Thromb Vasc Biol 2012;32:223-9.
Hofmann Bowman MA, Schmidt AM. S100/calgranulins EN-RAGEing the blood vessels: Implications for inflammatory responses and atherosclerosis. Am J Cardiovasc Dis 2011;1:92-100.
Caudrillier A, Mentaverri R, Brazier M, Kamel S, Massy ZA. Calcium-sensing receptor as a potential modulator of vascular calcification in chronic kidney disease. J Nephrol 2010;23:17-22.
Alam MU, Kirton JP, Wilkinson FL, Towers E, Sinha S, Rouhi M, et al.
Calcification is associated with loss of functional calcium-sensing receptor in vascular smooth muscle cells. Cardiovasc Res 2009;81:260-8.
Ivanovski O, Nikolov IG, Joki N, Caudrillier A, Phan O, Mentaverri R, et al.
The calcimimetic R-568 retards uremia-enhanced vascular calcification and atherosclerosis in apolipoprotein E deficient (apoE-/-) mice. Atherosclerosis 2009;205:55-62.
Hénaut L, Boudot C, Massy ZA, Lopez-Fernandez I, Dupont S, Mary A, et al.
Calcimimetics increase CaSR expression and reduce mineralization in vascular smooth muscle cells: Mechanisms of action. Cardiovasc Res 2014;101:256-65.
Parhami F, Tintut Y, Ballard A, Fogelman AM, Demer LL. Leptin enhances the calcification of vascular cells: Artery wall as a target of leptin. Circ Res 2001;88:954-60.
Zeadin M, Butcher M, Werstuck G, Khan M, Yee CK, Shaughnessy SG. Effect of leptin on vascular calcification in apolipoprotein E-deficient mice. Arterioscler Thromb Vasc Biol 2009;29:2069-75.
Hill J, Olson E, Griendling K, Kitsis R, Stull J. Muscle: Fundamental Biology and Mechanisms of Disease. Elsevier Science & Technology Books; 2012.
Doherty TM, Uzui H, Fitzpatrick LA, Tripathi PV, Dunstan CR, Asotra K, et al.
Rationale for the role of osteoclast-like cells in arterial calcification. FASEB J 2002;16:577-82.
Mozar A, Haren N, Chasseraud M, Louvet L, Mazière C, Wattel A, et al.
High extracellular inorganic phosphate concentration inhibits RANK-RANKL signaling in osteoclast-like cells. J Cell Physiol 2008;215:47-54.
Moe SM, O'Neill KD, Duan D, Ahmed S, Chen NX, Leapman SB, et al.
Medial artery calcification in ESRD patients is associated with deposition of bone matrix proteins. Kidney Int 2002;61:638-47.
Valdivielso JM. Vascular calcification: Types and mechanisms. Nefrologia 2011;31:142-7.
Prié D, Torres PU, Friedlander G. A new axis of phosphate balance control: Fibroblast growth factor 23-Klotho. Nephrol Ther 2009;5:513-9.
Hu P, Xuan Q, Hu B, Lu L, Wang J, Qin YH. Fibroblast growth factor-23 helps explain the biphasic cardiovascular effects of Vitamin D in chronic kidney disease. Int J Biol Sci 2012;8:663-71.
Toussaint ND, Pedagogos E, Tan SJ, Badve SV, Hawley CM, Perkovic V, et al.
Phosphate in early chronic kidney disease: Associations with clinical outcomes and a target to reduce cardiovascular risk. Nephrology (Carlton) 2012;17:433-44.
Parker BD, Schurgers LJ, Brandenburg VM, Christenson RH, Vermeer C, Ketteler M, et al.
The associations of fibroblast growth factor 23 and uncarboxylated matrix Gla protein with mortality in coronary artery disease: The Heart and Soul Study. Ann Intern Med 2010;152:640-8.
Massy ZA, Drüeke TB. Vascular calcification. Curr Opin Nephrol Hypertens 2013;22:405-12.
Lau WL, Leaf EM, Hu MC, Takeno MM, Kuro-o M, Moe OW, et al.
Vitamin D receptor agonists increase klotho and osteopontin while decreasing aortic calcification in mice with chronic kidney disease fed a high phosphate diet. Kidney Int 2012;82:1261-70.
Ketteler M, Bongartz P, Westenfeld R, Wildberger JE, Mahnken AH, Böhm R, et al.
Association of low fetuin-A (AHSG) concentrations in serum with cardiovascular mortality in patients on dialysis: A cross-sectional study. Lancet 2003;361:827-33.
Oikawa O, Higuchi T, Yamazaki T, Yamamoto C, Fukuda N, Matsumoto K. Evaluation of serum fetuin-A relationships with biochemical parameters in patients on hemodialysis. Clin Exp Nephrol 2007;11:304-8.
Heiss A, DuChesne A, Denecke B, Grötzinger J, Yamamoto K, Renné T, et al.
Structural basis of calcification inhibition by alpha 2-HS glycoprotein/fetuin-A. Formation of colloidal calciprotein particles. J Biol Chem 2003;278:13333-41.
Schafer C, Heiss A, Schwarz A, Westenfeld R, Ketteler M, Floege J, et al.
The serum protein alpha 2-Heremans-Schmid glycoprotein/fetuin-A is a systemically acting inhibitor of ectopic calcification. J Clin Invest 2003;112:357-66.
Price PA, Lim JE. The inhibition of calcium phosphate precipitation by fetuin is accompanied by the formation of a fetuin-mineral complex. J Biol Chem 2003;278:22144-52.
Smith ER, Hanssen E, McMahon LP, Holt SG. Fetuin-A-containing calciprotein particles reduce mineral stress in the macrophage. PLoS One 2013;8:e60904.
Lee CT, Chua S, Hsu CY, Tsai YC, Ng HY, Kuo CC, et al.
Biomarkers associated with vascular and valvular calcification in chronic hemodialysis patients. Dis Markers 2013;34:229-35.
Abdel-Wahab AF, Fathy O, Al-Harizy R. Negative correlation between fetuin-A and indices of vascular disease in systemic lupus erythematosus patients with and without lupus nephritis. Arab J Nephrol Transplant 2013;6:11-20.
Jung JY, Hwang YH, Lee SW, Lee H, Kim DK, Kim S, et al.
Factors associated with aortic stiffness and its change over time in peritoneal dialysis patients. Nephrol Dial Transplant 2010;25:4041-8.
Chen HY, Chiu YL, Hsu SP, Pai MF, Yang JY, Peng YS. Low serum fetuin A levels and incident stroke in patients with maintenance haemodialysis. Eur J Clin Invest 2013;43:387-96.
Maréchal C, Schlieper G, Nguyen P, Krüger T, Coche E, Robert A, et al.
Serum fetuin-A levels are associated with vascular calcifications and predict cardiovascular events in renal transplant recipients. Clin J Am Soc Nephrol 2011;6:974-85.
Giachelli CM, Steitz S. Osteopontin: A versatile regulator of inflammation and biomineralization. Matrix Biol 2000;19:615-22.
Scatena M, Liaw L, Giachelli CM. Osteopontin: A multifunctional molecule regulating chronic inflammation and vascular disease. Arterioscler Thromb Vasc Biol 2007;27:2302-9.
Speer MY, McKee MD, Guldberg RE, Liaw L, Yang HY, Tung E, et al.
Inactivation of the osteopontin gene enhances vascular calcification of matrix Gla protein-deficient mice: Evidence for osteopontin as an inducible inhibitor of vascular calcification in vivo
. J Exp Med 2002;196:1047-55.
Jono S, Peinado C, Giachelli CM. Phosphorylation of osteopontin is required for inhibition of vascular smooth muscle cell calcification. J Biol Chem 2000;275:20197-203.
Wada T, McKee MD, Steitz S, Giachelli CM. Calcification of vascular smooth muscle cell cultures: Inhibition by osteopontin. Circ Res 1999;84:166-78.
Qin X, Corriere MA, Matrisian LM, Guzman RJ. Matrix metalloproteinase inhibition attenuates aortic calcification. Arterioscler Thromb Vasc Biol 2006;26:1510-6.
Berezin AE, Kremzer AA. Circulating osteopontin as a marker of early coronary vascular calcification in type two diabetes mellitus patients with known asymptomatic coronary artery disease. Atherosclerosis 2013;229:475-81.
Tousoulis D, Siasos G, Maniatis K, Oikonomou E, Kioufis S, Zaromitidou M, et al.
Serum osteoprotegerin and osteopontin levels are associated with arterial stiffness and the presence and severity of coronary artery disease. Int J Cardiol 2013;167:1924-8.
Albu A, Fodor D, Bondor C, Craciun AM. Bone metabolism regulators and arterial stiffness in postmenopausal women. Maturitas 2013;76:146-50.
Kiefer FW, Zeyda M, Gollinger K, Pfau B, Neuhofer A, Weichhart T, et al.
Neutralization of osteopontin inhibits obesity-induced inflammation and insulin resistance. Diabetes 2010;59:935-46.
Zheng Y, Wang Z, Deng L, Yuan X, Ma Y, Zhang G, et al.
Osteopontin promotes inflammation in patients with acute coronary syndrome through its activity on IL-17 producing cells. Eur J Immunol 2012;42:2803-14.
Bazzichi L, Ghiadoni L, Rossi A, Bernardini M, Lanza M, De Feo F, et al.
Osteopontin is associated with increased arterial stiffness in rheumatoid arthritis. Mol Med 2009;15:402-6.
Sun J, Xu Y, Dai Z, Sun Y. Intermittent high glucose enhances proliferation of vascular smooth muscle cells by upregulating osteopontin. Mol Cell Endocrinol 2009;313:64-9.
Simonet WS, Lacey DL, Dunstan CR, Kelley M, Chang MS, Lüthy R, et al.
Osteoprotegerin: A novel secreted protein involved in the regulation of bone density. Cell 1997;89:309-19.
Collin-Osdoby P. Regulation of vascular calcification by osteoclast regulatory factors RANKL and osteoprotegerin. Circ Res 2004;95:1046-57.
Lacey DL, Timms E, Tan HL, Kelley MJ, Dunstan CR, Burgess T, et al.
Osteoprotegerin ligand is a cytokine that regulates osteoclast differentiation and activation. Cell 1998;93:165-76.
Bennett BJ, Scatena M, Kirk EA, Rattazzi M, Varon RM, Averill M, et al.
Osteoprotegerin inactivation accelerates advanced atherosclerotic lesion progression and calcification in older ApoE-/- mice. Arterioscler Thromb Vasc Biol 2006;26:2117-24.
Collin-Osdoby P, Rothe L, Bekker S, Anderson F, Huang Y, Osdoby P. Basic fibroblast growth factor stimulates osteoclast recruitment, development, and bone pit resorption in association with angiogenesis in vivo
on the chick chorioallantoic membrane and activates isolated avian osteoclast resorption in vitro
. J Bone Miner Res 2002;17:1859-71.
Bucay N, Sarosi I, Dunstan CR, Morony S, Tarpley J, Capparelli C, et al.
osteoprotegerin-deficient mice develop early onset osteoporosis and arterial calcification. Genes Dev 1998;12:1260-8.
Morony S, Sage AP, Corbin T, Lu J, Tintut Y, Demer LL. Enhanced mineralization potential of vascular cells from SM22a-Rankl (tg) mice. Calcif Tissue Int 2012;91:379-86.
Morena M, Jaussent I, Halkovich A, Dupuy AM, Bargnoux AS, Chenine L, et al.
Bone biomarkers help grading severity of coronary calcifications in non dialysis chronic kidney disease patients. PLoS One 2012;7:e36175.
van de Loo PG, Soute BA, van Haarlem LJ, Vermeer C. The effect of Gla-containing proteins on the precipitation of insoluble salts. Biochem Biophys Res Commun 1987;142:113-9.
Levy RJ, Gundberg C, Scheinman R. The identification of the Vitamin K-dependent bone protein osteocalcin as one of the gamma-carboxyglutamic acid containing proteins present in calcified atherosclerotic plaque and mineralized heart valves. Atherosclerosis 1983;46:49-56.
Hunter GK, Hauschka PV, Poole AR, Rosenberg LC, Goldberg HA. Nucleation and inhibition of hydroxyapatite formation by mineralized tissue proteins. Biochem J 1996;317(Pt 1):59-64.
Ducy P, Desbois C, Boyce B, Pinero G, Story B, Dunstan C, et al.
Increased bone formation in osteocalcin-deficient mice. Nature 1996;382:448-52.
Aoki A, Murata M, Asano T, Ikoma A, Sasaki M, Saito T, et al.
Association of serum osteoprotegerin with vascular calcification in patients with type 2 diabetes. Cardiovasc Diabetol 2013;12:11.
Kim KJ, Kim KM, Park KH, Choi HS, Rhee Y, Lee YH, et al.
Aortic calcification and bone metabolism: The relationship between aortic calcification, BMD, vertebral fracture, 25-hydroxyvitamin D, and osteocalcin. Calcif Tissue Int 2012;91:370-8.
Harmey D, Hessle L, Narisawa S, Johnson KA, Terkeltaub R, Millán JL. Concerted regulation of inorganic pyrophosphate and osteopontin by akp2, enpp1, and ank: An integrated model of the pathogenesis of mineralization disorders. Am J Pathol 2004;164:1199-209.
Rutsch F, Ruf N, Vaingankar S, Toliat MR, Suk A, Höhne W, et al.
Mutations in ENPP1 are associated with 'idiopathic' infantile arterial calcification. Nat Genet 2003;34:379-81.
Johnson K, Polewski M, van Etten D, Terkeltaub R. Chondrogenesis mediated by PPi depletion promotes spontaneous aortic calcification in NPP1-/- mice. Arterioscler Thromb Vasc Biol 2005;25:686-91.
Towler DA. Inorganic pyrophosphate: A paracrine regulator of vascular calcification and smooth muscle phenotype. Arterioscler Thromb Vasc Biol 2005;25:651-4.
O'Neill WC, Sigrist MK, McIntyre CW. Plasma pyrophosphate and vascular calcification in chronic kidney disease. Nephrol Dial Transplant 2010;25:187-91.
Riser BL, Barreto FC, Rezg R, Valaitis PW, Cook CS, White JA, et al.
Daily peritoneal administration of sodium pyrophosphate in a dialysis solution prevents the development of vascular calcification in a mouse model of uraemia. Nephrol Dial Transplant 2011;26:3349-57.
O'Neill WC, Lomashvili KA, Malluche HH, Faugere MC, Riser BL. Treatment with pyrophosphate inhibits uremic vascular calcification. Kidney Int 2011;79:512-7.
Villa-Bellosta R, Sorribas V. Calcium phosphate deposition with normal phosphate concentration. -Role of pyrophosphate-. Circ J 2011;75:2705-10.
Lomashvili KA, Monier-Faugere MC, Wang X, Malluche HH, O'Neill WC. Effect of bisphosphonates on vascular calcification and bone metabolism in experimental renal failure. Kidney Int 2009;75:617-25.
Zhou S, Fang X, Xin H, Guan S. Effects of alendronate on the Notch1-RBP-Jκ signaling pathway in the osteogenic differentiation and mineralization of vascular smooth muscle cells. Mol Med Rep 2013;8:89-94.
Villa-Bellosta R, Sorribas V. Prevention of vascular calcification by polyphosphates and nucleotides- role of ATP. Circ J 2013;77:2145-51.
Luo G, Ducy P, McKee MD, Pinero GJ, Loyer E, Behringer RR, et al.
Spontaneous calcification of arteries and cartilage in mice lacking matrix GLA protein. Nature 1997;386:78-81.
Khavandgar Z, Roman H, Li J, Lee S, Vali H, Brinckmann J, et al.
Elastin haploinsufficiency impedes the progression of arterial calcification in MGP-deficient mice. J Bone Miner Res 2014;29:327-37.
Moe SM, Reslerova M, Ketteler M, O'neill K, Duan D, Koczman J, et al.
Role of calcification inhibitors in the pathogenesis of vascular calcification in chronic kidney disease (CKD). Kidney Int 2005;67:2295-304.
Roy ME, Nishimoto SK. Matrix Gla protein binding to hydroxyapatite is dependent on the ionic environment: Calcium enhances binding affinity but phosphate and magnesium decrease affinity. Bone 2002;31:296-302.
Sweatt A, Sane DC, Hutson SM, Wallin R. Matrix Gla protein (MGP) and bone morphogenetic protein-2 in aortic calcified lesions of aging rats. J Thromb Haemost 2003;1:178-85.
Stenvinkel P, Ketteler M, Johnson RJ, Lindholm B, Pecoits-Filho R, Riella M, et al.
IL-10, IL-6, and TNF-alpha: Central factors in the altered cytokine network of uremia – The good, the bad, and the ugly. Kidney Int 2005;67:1216-33.
Watson KE, Parhami F, Shin V, Demer LL. Fibronectin and collagen I matrixes promote calcification of vascular cells in vitro
, whereas collagen IV matrix is inhibitory. Arterioscler Thromb Vasc Biol 1998;18:1964-71.
Watson KE, Boström K, Ravindranath R, Lam T, Norton B, Demer LL. TGF-beta 1 and 25-hydroxycholesterol stimulate osteoblast-like vascular cells to calcify. J Clin Invest 1994;93:2106-13.
Shioi A, Katagi M, Okuno Y, Mori K, Jono S, Koyama H, et al.
Induction of bone-type alkaline phosphatase in human vascular smooth muscle cells: Roles of tumor necrosis factor-alpha and oncostatin M derived from macrophages. Circ Res 2002;91:9-16.
Jono S, Nishizawa Y, Shioi A, Morii H. 1,25-Dihydroxyvitamin D3 increases in vitro
vascular calcification by modulating secretion of endogenous parathyroid hormone-related peptide. Circulation 1998;98:1302-6.
Ducy P, Zhang R, Geoffroy V, Ridall AL, Karsenty G. Osf2/Cbfa1: A transcriptional activator of osteoblast differentiation. Cell 1997;89:747-54.
Tyson KL, Reynolds JL, McNair R, Zhang Q, Weissberg PL, Shanahan CM. Osteo/chondrocytic transcription factors and their target genes exhibit distinct patterns of expression in human arterial calcification. Arterioscler Thromb Vasc Biol 2003;23:489-94.
Li X, Yang HY, Giachelli CM. BMP-2 promotes phosphate uptake, phenotypic modulation, and calcification of human vascular smooth muscle cells. Atherosclerosis 2008;199:271-7.
Abe E, Yamamoto M, Taguchi Y, Lecka-Czernik B, O'Brien CA, Economides AN, et al.
Essential requirement of BMPs-2/4 for both osteoblast and osteoclast formation in murine bone marrow cultures from adult mice: Antagonism by noggin. J Bone Miner Res 2000;15:663-73.
Yao Y, Bennett BJ, Wang X, Rosenfeld ME, Giachelli C, Lusis AJ, et al.
Inhibition of bone morphogenetic proteins protects against atherosclerosis and vascular calcification. Circ Res 2010;107:485-94.
Chen D, Zhao M, Mundy GR. Bone morphogenetic proteins. Growth Factors 2004;22:233-41.
Wang EA, Rosen V, D'Alessandro JS, Bauduy M, Cordes P, Harada T, et al.
Recombinant human bone morphogenetic protein induces bone formation. Proc Natl Acad Sci U S A 1990;87:2220-4.
Balemans W, Ebeling M, Patel N, Van Hul E, Olson P, Dioszegi M, et al.
Increased bone density in sclerosteosis is due to the deficiency of a novel secreted protein (SOST). Hum Mol Genet 2001;10:537-43.
Brunkow ME, Gardner JC, Van Ness J, Paeper BW, Kovacevich BR, Proll S, et al.
Bone dysplasia sclerosteosis results from loss of the SOST gene product, a novel cystine knot-containing protein. Am J Hum Genet 2001;68:577-89.
Joiner DM, Ke J, Zhong Z, Xu HE, Williams BO. LRP5 and LRP6 in development and disease. Trends Endocrinol Metab 2013;24:31-9.
Krishnan V, Bryant HU, Macdougald OA. Regulation of bone mass by Wnt signaling. J Clin Invest 2006;116:1202-9.
Robling AG, Niziolek PJ, Baldridge LA, Condon KW, Allen MR, Alam I, et al.
Mechanical stimulation of bone in vivo
reduces osteocyte expression of Sost/sclerostin. J Biol Chem 2008;283:5866-75.
Koos R, Brandenburg V, Mahnken AH, Schneider R, Dohmen G, Autschbach R, et al.
Sclerostin as a potential novel biomarker for aortic valve calcification: An in-vivo
study. J Heart Valve Dis 2013;22:317-25.
Hampson G, Edwards S, Conroy S, Blake GM, Fogelman I, Frost ML. The relationship between inhibitors of the Wnt signalling pathway (Dickkopf-1(DKK1) and sclerostin), bone mineral density, vascular calcification and arterial stiffness in post-menopausal women. Bone 2013;56:42-7.
Szulc P, Bertholon C, Borel O, Marchand F, Chapurlat R. Lower fracture risk in older men with higher sclerostin concentration: A prospective analysis from the MINOS study. J Bone Miner Res 2013;28:855-64.
Morales-Santana S, García-Fontana B, García-Martín A, Rozas-Moreno P, García-Salcedo JA, Reyes-García R, et al.
Atherosclerotic disease in type 2 diabetes is associated with an increase in sclerostin levels. Diabetes Care 2013;36:1667-74.
Kong YY, Boyle WJ, Penninger JM. Osteoprotegerin ligand: A regulator of immune responses and bone physiology. Immunol Today 2000;21:495-502.
Kong YY, Feige U, Sarosi I, Bolon B, Tafuri A, Morony S, et al.
Activated T cells regulate bone loss and joint destruction in adjuvant arthritis through osteoprotegerin ligand. Nature 1999;402:304-9.
Anderson DM, Maraskovsky E, Billingsley WL, Dougall WC, Tometsko ME, Roux ER, et al.
A homologue of the TNF receptor and its ligand enhance T-cell growth and dendritic-cell function. Nature 1997;390:175-9.
Myers DE, Collier FM, Minkin C, Wang H, Holloway WR, Malakellis M, et al.
Expression of functional RANK on mature rat and human osteoclasts. FEBS Lett 1999;463:295-300.
Green EA, Flavell RA. TRANCE-RANK, a new signal pathway involved in lymphocyte development and T cell activation. J Exp Med 1999;189:1017-20.
Kanegae Y, Tavares AT, Izpisúa Belmonte JC, Verma IM. Role of Rel/NF-kappaB transcription factors during the outgrowth of the vertebrate limb. Nature 1998;392:611-4.
Yasuda H, Shima N, Nakagawa N. Osteoclast differentiation factor is a ligand for osteoprotegerin/osteoclastogenesis-inhibitory factor and is identical to TRANCE/RANKL. Proc Natl Acad Sci U S A 1998;95:3597-602.
Morena M, Terrier N, Jaussent I, Leray-Moragues H, Chalabi L, Rivory JP, et al.
Plasma osteoprotegerin is associated with mortality in hemodialysis patients. J Am Soc Nephrol 2006;17:262-70.
Hwang JJ, Wei J, Abbara S, Grinspoon SK, Lo J. Receptor activator of nuclear factor-κB ligand (RANKL) and its relationship to coronary atherosclerosis in HIV patients. J Acquir Immune Defic Syndr 2012;61:359-63.
Ozkok A, Caliskan Y, Sakaci T, Erten G, Karahan G, Ozel A, et al.
Osteoprotegerin/RANKL axis and progression of coronary artery calcification in hemodialysis patients. Clin J Am Soc Nephrol 2012;7:965-73.
Morena M, Dupuy AM, Jaussent I, Vernhet H, Gahide G, Klouche K, et al.
A cut-off value of plasma osteoprotegerin level may predict the presence of coronary artery calcifications in chronic kidney disease patients. Nephrol Dial Transplant 2009;24:3389-97.
Meneghini M, Regalia A, Alfieri C, Barretta F, Croci D, Gandolfo MT, et al.
Calcium and osteoprotegerin levels predict the progression of the abdominal aortic calcifications after kidney transplantation. Transplantation 2013;96:42-8.
Svensson M, Dahle DO, Mjøen G, Weihrauch G, Scharnagl H, Dobnig H, et al.
Osteoprotegerin as a predictor of renal and cardiovascular outcomes in renal transplant recipients: Follow-up data from the ALERT study. Nephrol Dial Transplant 2012;27:2571-5.
Gordin D, Soro-Paavonen A, Thomas MC, Harjutsalo V, Saraheimo M, Bjerre M, et al.
Osteoprotegerin is an independent predictor of vascular events in Finnish adults with type 1 diabetes. Diabetes Care 2013;36:1827-33.
Winther S, Christensen JH, Flyvbjerg A, Schmidt EB, Jørgensen KA, Skou-Jørgensen H, et al.
Osteoprotegerin and mortality in hemodialysis patients with cardiovascular disease. Clin Nephrol 2013;80:161-7.
Scialla JJ, Leonard MB, Townsend RR, Appel L, Wolf M, Budoff MJ, et al.
Correlates of osteoprotegerin and association with aortic pulse wave velocity in patients with chronic kidney disease. Clin J Am Soc Nephrol 2011;6:2612-9.
Bleyer AJ, Burke SK, Dillon M, Garrett B, Kant KS, Lynch D, et al.
A comparison of the calcium-free phosphate binder sevelamer hydrochloride with calcium acetate in the treatment of hyperphosphatemia in hemodialysis patients. Am J Kidney Dis 1999;33:694-701.
Cozzolino M, Staniforth ME, Liapis H, Finch J, Burke SK, Dusso AS, et al.
Sevelamer hydrochloride attenuates kidney and cardiovascular calcifications in long-term experimental uremia. Kidney Int 2003;64:1653-61.
Chertow G, Burke S, Raggi P, Chasan-Taber S, Bommer J, Holzer H. Determinants of progressive vascular calcification in hemodialysis patients. Kidney Int 2002;62:245-52.
Holick MF. Vitamin D deficiency. N Engl J Med 2007;357:266-81.
Naves-Díaz M, Alvarez-Hernández D, Passlick-Deetjen J, Guinsburg A, Marelli C, Rodriguez-Puyol D, et al.
Oral active Vitamin D is associated with improved survival in hemodialysis patients. Kidney Int 2008;74:1070-8.
Teng M, Wolf M, Ofsthun MN, Lazarus JM, Hernán MA, Camargo CA Jr., et al.
Activated injectable Vitamin D and hemodialysis survival: A historical cohort study. J Am Soc Nephrol 2005;16:1115-25.
Lopez I, Aguilera-Tejero E, Mendoza FJ, Almaden Y, Perez J, Martin D, et al.
Calcimimetic R-568 decreases extraosseous calcifications in uremic rats treated with calcitriol. J Am Soc Nephrol 2006;17:795-804.
Lopez I, Mendoza FJ, Guerrero F, Almaden Y, Henley C, Aguilera-Tejero E, et al.
The calcimimetic AMG 641 accelerates regression of extraosseous calcification in uremic rats. Am J Physiol Renal Physiol 2009;296:F1376-85.
Budoff MJ, Lane KL, Bakhsheshi H, Mao S, Grassmann BO, Friedman BC, et al.
Rates of progression of coronary calcium by electron beam tomography. Am J Cardiol 2000;86:8-11.
Callister T, Raggi P, Cooil B, Lippolis N, Russo D. Coronary artery disease: Improved reproducibility of calcium scoring with an electron-beam CT volumetric method. N Engl J Med 1998;339:1972-8.
Tamashiro M, Iseki K, Sunagawa O, Inoue T, Higa S, Afuso H, et al.
Significant association between the progression of coronary artery calcification and dyslipidemia in patients on chronic hemodialysis. Am J Kidney Dis 2001;38:64-9.
Ishimura E, Okuno S, Taniwaki H, Kizu A, Tsuchida T, Shioi A, et al.
Different risk factors for vascular calcification in end-stage renal disease between diabetics and nondiabetics: The respective importance of glycemic and phosphate control. Kidney Blood Press Res 2008;31:10-5.
Ishimura E, Okuno S, Kitatani K, Kim M, Shoji T, Nakatani T, et al.
Different risk factors for peripheral vascular calcification between diabetic and non-diabetic haemodialysis patients – Importance of glycaemic control. Diabetologia 2002;45:1446-8.
Sabbagh Y, Graciolli FG, O'Brien S, Tang W, dos Reis LM, Ryan S, et al.
Repression of osteocyte Wnt/ß-catenin signaling is an early event in the progression of renal osteodystrophy. J Bone Miner Res 2012;27:1757-72.